High-frequency heating apparatus

ABSTRACT

A high-frequency heating apparatus includes a supply source for supplying high-frequency energy into a conductive heating chamber. Two pairs of stirring blades mounted on a rotary shaft inside the chamber are positioned relatively to the supply source so that a substantial portion of the radiated energy is intercepted and reflected by the blades to afford more uniform heating of materials within the chamber. The generally elongated stirring blades are mounted tangentially of the circumference of an imaginary circle lying in a plane normal to the rotary shaft and concentric with the shaft axis. The blades of each pair lie in parallel planes inclined at an angle of 45* with respect to the plane of the imaginary circle and thus are oppositely inclined with respect to the axis of the rotary shaft. As the blades are rotated, high-frequency energy from the source, in a first mode, is reflected from the upper surface of one of the blades of the pair in a centrifugal direction and, in a second mode, from the upper surface of the other blade in a centripital direction toward the first blade of the pair and reflected downwardly from the lower surface of the latter. Continuous rotation of the shaft effects a continuously alternating sequence of the modes thus established by each pair of blades.

United States Patent [72] Inventor Michio Funahashi Otsu, Japan [21Appl. No. 36,007 [22] Filed May 11, 1970 [45] Patented Dec. 7, 1971 [73]Assignee Sanyo Electric Co., Ltd.

0saka-iu, Japan [32] Priority May 14, 1969 [3 3] Japan [31 44/44857 [54]HIGH-FREQUENCY HEATING APPARATUS 12 Claims, 5 Drawing Figs.

[52] U.S.Cl 219/1055, 219/1057 [51] Int. Cl 1105b 9/06,

H05b 1/00 [50] Field of Search 2 l 9/1055 [56] References Cited UNITEDSTATES PATENTS 3,431,381 3/1969 Anderson.... 219/10.55 3,364,332 1/1968Raftmark 219/1055 2,813,185 219/1055 11/1957 Smith Primary Examiner-J.V. Truhe Assistant ExaminerL. H. Bender Anorney-Brufsky, Staas, Breiner& Halsey ABSTRACT: A high-frequency heating apparatus includes a supplysource for supplying high-frequency energy into a conductive heatingchamber. Two pairs of stirring blades mounted on a rotary shaft insidethe chamber are positioned relatively to the supply source so that asubstantial portion of the radiated energy is intercepted and reflectedby the blades to afford more uniform heating of materials within thechamber. The generally elongated stirring blades are mountedtangentially of the circumference of an imaginary circle lying in aplane normal to the rotary shaft and concentric with the shaft axis. Theblades of each pair lie in parallel planes inclined at an angle of 45with respect to the plane of the imaginary circle and thus areoppositely inclined with respect to the axis of the rotary shaft. As theblades are rotated, highfrequency energy from the source, in a firstmode, is reflected from the upper surface of one of the blades of thepair in a centrifugal direction and, in a second mode, from the uppersurface of the other blade in a centripital direction toward the firstblade of the pair and reflected downwardly from the lower surface of thelatter. Continuous rotation of the shaft effects a continuouslyalternating sequence of the modes thus established by each pair ofblades.

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SHEET 3 [IF 3 INVENTOR MICHIO FUNAHASHI Brats/c4 8mm irum Hutu ATTORNEYSl HIGH-FREQUENCY HEATING APPARATUS BACKGROUND OF THE INVENTION Field ofthe Invention This invention relates to high-frequencyheating apparatusand more specifically to means for improving the highfrequencyelectromagnetic field distribution or mode pattern by stirrer meanswhich produce a continuously alternating sequence of different modepatterns to achieve more uniform heating.

Description of the Prior Art In high-frequency heating apparatus, whichhas now found wide use, materials are'heated or cooked by applyinghighfrequency energy tothe materials. The heating or cooking is achieveddue to the dielectric loss presented by the materials to thehigh-frequency energy, as is well known. The heating apparatus of thistype includes a'cubiforrn cavity or oven of conductive, typicallymetallic, material, and a supply source for supplying high-frequencyenergy into the cavity. One of the walls of the oven defining the cubiccavity is constructed as a door providing access to the cavity andwhich, when shut, effects a suitable seal of the cavity.

In such high-frequency heating apparatus, the oven is considered asdefining ahigh Q resonant cavity. As is well known, the higher the'Q ofthe resonant cavity, the more well defined are the'modes of the fieldsestablished within the cavity resulting in a more uneven heating withinthe cavity with respect to its spatial dimensions. When only asmallheating load is presented to the oven, such as when only a small amountof material is placed in the oven for heating, the effective of theresonant cavity remains relatively high resulting in uneven heating. Thesmaller the heating load, therefore, the less uniform the heatingbecomes. On the contrary, as the heating load is increased, the numberof high-frequency electromag-. netic field modes generated within theoven are correspondingly increased, and more uniform heating of thematerials is achieved. 7

Since controlof the number of electromagnetic field modes cannot beachieved'in a practical sense by always supplying a high heating load tothe oven and further since it is desirable to improve the uniformity ofheating even in the presence of high heating loads, there have beenprovided and proposed heretofore in the prior art various types ofmovable devices for increasing the number of electromagnetic field modeswithin such heating apparatus'Such mode changing devices, in addition toexciting different modes, also serve to redirect the radiated energy byreflection toeffect more uniform heating, a matter of greater importancein the high load situation.

One such prior art device comprises a propeller-type fan comprising aplurality of radially extending blades of conductive or metallicmaterials, inclined relatively to the axis of rotation much like theblades of a conventional airplane propeller. The propeller is positionedsuch that the blades are opposite to a high-frequency energy source forintercepting and reflecting the energy propagated into the oven, the fanbeing continuously rotated by a suitable motor. As the fan is rotated,the high-frequency energy is reflected from each blade in succession asit is advanced into position opposite the energy source, producing alarger number of modes within the cavity of the oven. Such apropeller-type fan, however, provides for reflection of thehigh-frequency energy only in a predetermined direction and in apredetermined cycle, and therefore has not been capable of providing thedesired effect of uniformheating to a sufficient extent.

In US. Pat. No. 2,813,185 entitled Heating Device" and issued to R. V.Smith in l957, there is disclosed high-frequency heating apparatusincluding a movable device positioned to provide an increased number ofmodes to afford more uniform heating. The movable device thereindisclosed includes a propeller-type fan comprising a plurality ofsimilar blades mounted on a rotary shaft and extending radially from theshaft. A motor rotates the fan for continuously advancing the blades toa position opposite to a high-frequency energy source, thereby tointercept and reflect the propagated ener gy. A first set of blades areinclined to a plane normal to the axis of the shaft at a first angle anda second set of blades are of the opposite or reversed inclination withrespect to that same plane relative to the first set of blades. Thus, asthe blades are rotated into position for intercepting the energy, thefirst set reflects the energy in a corresponding first direction and theblades of the other set reflect the energy in a corresponding, oppositedirection. By alternating the blades of opposite inclination, therotation of the propeller-type device effects a continuous, periodicreflection of the energy in the noted opposite directions. Although thedevice of the referenced patent affords some improvement over the otherprior art devices, it provides an insufficient degree of uniform heatingsince the energy is only reflected in the noted two opposite directions.

Thus, the prior art has failed to provide a device of relatively simpleconstruction capable of producing a large number of electromagneticfield modes for attaining uniform heating in resonant cavity-typeheating ovens. The invention disclosed herein accomplishes this purpose.

SUMMARY OF THE INVENTION The invention comprises a movable device to bemounted within the resonant cavity of a heating chamber to effectreflection of high frequency energy propagated into the cavity and toestablish an increased number of electromagnetic field modes to assureuniform heating of materials within the cavity. The device comprises atleast one pair of blades mounted on a rotary shaft, the generallyelongated blades thereby being positioned tangentially of thecircumference of an imaginary circle lying on a plane normal to therotary shaft and concentric with the shaft axis. The blades of each pairlie in parallel planes inclined at an angle of 45 with respect to theplane of the imaginary circle and thus are oppositely inclined withrespect to the axis of the rotary shaft. Thus, the plane of one bladeintersects the axis at a point above the plane of the imaginary circlewhereas the plane of the other blade intersects the axis at a pointbelow the plane of the imaginary circle. A prime mover such as asuitable motor is attached to the shaft to rotate it and the bladesmounted on it, the blade positions being selected relatively to thesource of electromagnetic energy propagated into the chamber such thatthe blades successively are rotated into position opposite the source tointercept and reflect the energy propagated into the chamber.

Assuming that the energy is directed into the cavity from above and in adirection parallel to the axis of the rotary shaft, one of the blades ofthe pair, as above described, reflects the energy from an upper surfacethereof in a centrifugal direction and thus radially outwardly withrespect to the shaft. As the other blade of the pair is advanced intoposition, high-frequency energy is reflected from the upper surfacethereof in a centripetal direction or radially inward direction towardthe lower surface of the first-mentioned blade positioned on thediametrically opposite side of the shaft. Acertain amount of thehighfrequency energy then is reflected from that lower surface of thefirst-mentioned blade in a vertically downward direction again parallelto the axis of the shaft.

Thus, in the first mode of operation, the high-frequency energy isreflected in the centrifugal direction with respect to the rotary shaftof the movable device, whereas in the second mode of operation, thehigh-frequency energy is reflected in the centripetal direction of theshaft of the movable device and a certain amount of the high-frequencyenergy is reflected downward (or upward depending on the design) or inparallel to the rotary shaft. This diversified transmitting route of thehigh-frequency energy results in a larger number of electromagneticfield modes and more uniform heating as compared with any of theconventional type devices.

Therefore, an object of this invention is to provide a highfrequencyheating apparatus including a movable device which provides improvedheating patterns.

Another object of this invention is to provide a movable device in ahigh-frequency heating apparatus for creating an increased number ofdiversified electromagnetic field modes.

A further object of this invention is to ultimately directhigh-frequency energy in centrifugal and centripetal directions from thecircumference of an imaginary circle coaxial with the axis of a shaftsupporting the movable device.

Still a further object of this invention is to provide a movable devicein a high-frequency heating apparatus to ultimately directhigh-frequency energy introduced into the apparatus in centrifugal andcentripetal directions with respect to a rotary shaft of the movabledevice and to further direct the highfrequency energy directed to thecentripetal direction in a direction parallel to the axis of the rotaryshaft.

Still a further object of this invention is to provide a movable devicein a high-frequency heating apparatus having blades extendingtangentially of the circumference of an imaginary circle coaxial withthe axis of the rotary shaft supporting the device.

Yet a further object of this invention is to provide a movable device ina high-frequency heating apparatus having a plurality of stirring bladesextending tangentially of the circumference of the imaginary circlenormal to and coaxial with the axis of a rotary shaft supporting thedevice and having selected ones of the blades inclined in a firstdirection and the other blades inclined in an opposite direction withrespect to the plane of the imaginary circle as the blades are rotatedabout the circumference of that circle into position for interceptingthe high-frequency energy propagated into the apparatus.

These objects and other objects and features of the invention will beapparent and more fully understood from the following description of theinvention made with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS:

FIG. 1 is a cross-sectional view of high-frequency heating apparatus towhich this invention is applied;

FIG. 2 is a top view of a movable high-frequency reflecting device inaccordance with this invention;

FIG. 3 is a sectional view of the device shown in FIG. 2 along the lineIII-III;

FIG. 4 is a diagrammatic, cross-sectional view of the cavity of thehigh-frequency heating apparatus, employed for explaining the first modeof operation of the apparatus of this invention; and

FIG. 5 is a view similar to FIG. 4 in which the reflecting device hasbeen rotated to a different position than in FIG. 4 for explanation ofthe second mode of operation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS:

FIG. 1 is a sectional view of a typical example of the highfrequencyheating apparatus to which this invention is applied. Referring to FIG.1, the high-frequency energy generated at a magnetron l is transmittedthrough a waveguide 2 to the cubic or cubiform heating chamber 3, orcavity, made of a conductive material. The heating chamber 3 includes aninlet or opening 4 for inserting materials to be heated or cooked intothe chamber. The inlet 4 is provided with a door 8, which can be openedor closed freely, and which when closed provides a perfect seal withrespect to the high-frequency energy generated within the chamber 3.

Considering merely the chamber 3 with means for introducing highfrequency energy into that chamber such as from waveguide 2 and in theabsence of any further energy controlling device, a substantially unevenor nonuniform distribution of the electromagnetic field would beestablished in the heating chamber 3. Any materials placed within thechamber 3 would be heated very unevenly, the degree of the unevenheating increasing, the smaller the heating load or materials provided.

As generally recognized heretofore in the prior art, to provide moreeven heating, a stirring blade 6 made of conductive material is providedin the vicinity of an outlet 5 of waveguide 2. The blade 6 is rotated bymeans of a motor 7 disposed outside the heating chamber 3. Thehigh-frequency energy is reflected and dispersed by the stirring bladeand the distribution of high-frequency energy impinging upon thematerials to be heated, is thus made more even. In others words, thenumber of electromagnetic field modes of the high-frequency energy inthe heating chamber 3 or cavity is increased.

The present invention provides for a stirring blades of improvedconstruction which increases the stirring or distribution effect of theblade to provide increased reflections and an increased number ofelectromagnetic field modes thereby to afford more uniform distributionof the field and more uniform heating. The details of the blades areillustrated in FIGS. 2 and 3. FIG. 2 is a top view of an electromagneticfield stirring blade of an embodiment constructed in accordance withthis invention. FIG. 3 is a sectional view of the blade of FIG. 2 alongthe line III-III.

With reference to FIG. 2, the movable device or electromagnetic fieldfan of the invention includes a boss 10 by which the fan is affixed to arotary shaft and to which are secured arms 11, such as by spot welding,extending radially of the boss 10 and thus of the axis of the rotaryshaft. As shown, the arms 11 extend diametrically of that axis and atright angles to one another. Mounted on the opposite ends of each arm 11are blades 12 and 12' which extend tangentially of the circumference ofan imaginary circle C lying in a plane normal to the axis and coaxialwith the axis. The blades 12 and 12 may be affixed to the ends of therespective arms 11 by spot welding or other suitable technique.

The pair of blades 12 and'l2 associated with each arm 11, as best shownin FIG. 3, are generally parallel to one another, that is, the blades 12and 12' generally lie in planes which are parallel to one another andwhich are thus oppositely inclined with respect to the axis of the fan.This is illustrated by the representation of the plane in which theblade 12 generally lies, intersecting the axis at the point P1 above theplane of the imaginary circle and by the plane in which the blade 12'generally lies, intersecting that same axis at the point P2 below theplane of the imaginary circle, the angles defined by the intersectionsof the axis and the plane in each instance being approximately 45. Inthus defining the inclination of the blades 12 and 12, of course, thereis no intent to limit the specific configuration of the blades toprecisely planar form although generally they may be considered as lyingwithin mutually parallel planes. The arm 11 may conveniently be providedwith a bent terminal portion or end to which the blade 12' is mounted atone end thereof, and with an inverse V-shaped bent portion 11' at thediametrically opposite end thereof for supporting the blade 12 wherebythe blades 12 and 12' are supported generally in the vicinity of theplane of the imaginary circle C as illustrated in FIG. 2.

The modes of operation of the electromagnetic field stirring by thestirring blades of this invention may be understood more fully withreference to FIGS. 4 and 5. By connecting the boss 10 of the fan 13 ofthis invention to the prime mover 15 such as a suitable motor, placedoutside the heating chamber 14, rotation is effected in such a way thateach stirring blade 12 or 12' is brought, in succession, to a positionopposite the output opening 16 of the waveguide.

FIG. 4 shows the position of the blade in the cavity 14 at a time whenthe blade 12, the plane of which intersects the axis of rotation abovethe plane of the imaginary circle C as illustrated in FIG. 3, ispositioned opposite the output opening 16 of the waveguide. In thiscontext, the waveguide is such as that diagrammatically illustrated inFIG. 1 identified by the numeral 2. A material 18 to be heated is shownplaced in the cavity 14, supported above the bottom by means of the bedplate 17 of a material transparent to the high-frequency energy, such asglass. As readily seen from FIG. 4, the highfrequency energy from theoutput opening 16 of the waveguide is reflected from the upper surfaceof the blade 12 and is directed radially or in the centrifugal directionwith respect to the axis of the rotary shaft. The geometry and overalldimensions of the stirring blades 12 and 12' are preferably selected inrelation to the dimensions of the output opening 16 of the waveguidesuch that the length of the blade 12 in the dimension disposedtangentially of the imaginary circle C is somewhat less than that of theopening 16. By this technique, a portion of the high-frequency energyradiated from the output opening 16 of the waveguide is not interceptedby the waveguide but rather propagates in a downward direction generallyparallel to the axis of rotation for directly heating the material 18.

FIG. 5 is a diagrammatic illustration of the heating apparatussubstantially identical to that of FIG. 4 but in which the fan 13 hasbeen rotated substantially 180 to position the blade 12' opposite theoutput opening 16 of the waveguide and thus in position for interceptingand reflecting energy propagated therethrough. The blade 12' as definedin FIG. 3 lies in a plane which intersects the axis of rotation at apoint below the plane of the imaginary circle. As readily seen from FIG.5, a portion of the high-frequency energy radiated from the outputopening 16 of the waveguide is reflected from the upper surface of thisstirring blade 12' in the centripetal direction with respect to therotary shaft, or axis of rotation, and is further reflected downwardfrom the lower surface of the stirring blade 12 which is diametricallyopposite to the blade 12' and thus toward the material 18 to be heated.In this instance, it is understood that the relatively narrow armconnecting the blade 12 to the boss presents only a minimal surfacerelative to the surface of the blade 12 and thus permits a substantialportion of the high-frequency energy thus reflected from the uppersurface of the blade 12' to be directed to and reflected downwardly fromthe lower surface of the blade 12. In addition, a portion of thehigh-frequency energy transmitted through the opening 16, as in the caseof the blade 12 discussed in FIG. 4, is not intercepted by the blade 12'and travels directly downwardly and thus in a direction generallyparallel to the axis of rotation; further, a portion of the energyreflected from the blade 12' is not intercepted and reflected by thelower surface of blade 12, but rather continues in a straight path andthus in a radial direction relative to the rotary shaft.

The apparatus of the invention, due to the continuous rotation of thedevice 13, effects a continuously repeating alternating sequence of themodes of operation described in reference to FIGS. 4 and 5 and inaddition produces intermediate modes in the transitions from either ofthe two major modes as described. As a result, a substantialdiversification of the electromagnetic field modes is generated in thecavity. The diversification of the modes and the reflections of theenergy thus provided contributes to a substantial improvement in thedegree of uniformity of the electromagnetic field produced within theheating chamber and thus to more unifonn heating of materials placedtherein.

This effect was substantiated by experimental data obtained by theinventor in comparing the uniformity of heating achieved in anelectromagnetic heating apparatus employing the movable device, orstirring blades, of the invention with that achieved in such apparatusemploying conventional electromagnetic field stirring blades such asthose described above in relation to the prior art. The data wasobtained in accordance with the following procedure.

Twelve glass cups each containing I00 cc. of water were placed in theheating chamber, the cups being disposed in three columns and in fourlines. These cups were subjected to the high-frequency energy for twominutes in the chamber. Then, the temperature of the water in each cupwas measured. The results were as follows:

For this apparatus of the prior art the maximum temperature was 21.7 C.and the minimum temperature 8.7 C. and the difference between the twowas 13 C. while for the apparatus of this invention the maximumtemperature was 16.8 C. and the minimum temperatures was 11.0 C. and thedifference between the two was 5.8 C. These results clearly demonstratethat the uniformity of the field and resultant uniform heating achievedwhen employing the device of the invention provides a substantialimprovement over that obtained with the conventional prior art devices.

While specific preferred embodiments of the invention have beendescribed, it will be apparent that obvious variations and modificationsof the invention will occur to those of ordinary skill in the art from aconsideration of the foregoing description. It is therefore desired thatthe present invention be limited only by the appended claims.

What is claimed is: I

l. A device for use in a high-frequency heating apparatus having anenclosure made of conductive material into which high-frequency energyis supplied for heating material placed within the enclosure comprising:

a pair of blades of conductive material,

means for mounting said blades within said enclosure for rotation abouta predetermined axis of rotation, said blades being rotatable insuccession into position to intercept a portion of the high-frequencyenergy supplied into the enclosure,

one of said blades being positioned by said mounting means to directhigh-frequency energy intercepted thereby in a centrifugal directionwith respect to said axis of rotation,

the other of said pair of blades being positioned by said mounting meansto direct high-frequency energy intercepted thereby in the centripetaldirection with respect to said axis of rotation, and

said one of said blades furthermore is positioned for interceptingenergy directed centripetally from said other of said blades anddirecting a portion of said centripetally directed energy parallel tothe axis of rotation.

2. A device as recited inclaim 1 wherein said blades of said pairthereof are mounted at diametrically opposite positions relative to theaxis of rotation and tangentially of the circumference of an imaginarycircle concentric with the axis of rotation and in a plane normalthereto, and

said pair of blades are oppositely inclined with respect to the plane ofthe imaginary circle relative to the axis of rotation.

3. The device as recited in claim 2 wherein said blades lie insubstantially parallel planes inclined to the plane of the imaginarycircle at an angle of approximately 45.

4. A device as recited in claim 2 wherein said blades define planesintersecting the axis of rotation on opposite sides of the plane of theimaginary circle at angles of approximately 45.

5. A device as recited in claim 2 wherein said blades are each ofelongated configuration and are positioned along a given dimensionthereof tangentially of the circumference of the imaginary circle.

6. A device as recited in claim 1 wherein there is further provided atleast one additional pair of said blades mounted on said rotary shaftwith the blades of each pair diametrically disposed about said shaft andwith said pairs of blades equiangularly disposed about said shaft.

7. A high-frequency heating apparatus comprising:

an enclosure made of a conductive material,

means for supplying high-frequency energy to said enclosure,

means for placing a heating load within said enclosure to be heated bythe high-frequency energy,

a movable device and means including a rotary shaft to which said deviceis mounted for rotating said device within said enclosure,

said movable device includes a pair of conductive blades rotatable insuccession into position to intercept a portion of high-frequency energysupplied to the enclosure,'one of said pair of blades directinghigh-frequency energy intercepted thereby in a centrifugal directionwith respect to said rotary shaft and the other of said pair of bladesdirecting high-frequency intercepted thereby in a centripetal directionwith respect to the rotary shaft, and

said one of said blades furthermore is positioned for interceptingenergy directed centripetally from said other of said blades anddirecting a portion of said centripetally directed energy parallel tothe axis of rotation.

8. Apparatus as recited in claim 7 wherein said blades of said pairthereof are mounted at diametrically opposite positions relative to saidrotary shaft and tangentially of the circumference of an imaginarycircle concentric with the axis of rotation of said shaft and in a planenormal thereto, and

said pair of blades are oppositely inclined with respect to the plane ofthe imaginary circle and axis of rotation.

9. Apparatus as recited in claim 8 wherein said blades are mounted bysaid mounting means to lie in substantially parallel planes inclined tothe plane of the imaginary circle at an angle of approximately 45.

10. Apparatus as recited in claim 8 wherein said blades define planesintersecting the axis of rotation of said rotary shaft on opposite sidesof the plane of the imaginary circle at angles of approximately 45.

11. Apparatus as recited in claim 8 wherein said blades are positionedabove a given dimensions thereof tangentially of the circumference ofthe imaginary circle.

12. Apparatus as recited in claim 7 wherein said movable device furtherincludes at least one additional pair of said blades mounted on saidrotary shaft with the blades of each pair diametrically disposed aboutsaid shaft and with said pairs of blades equian gularly disposed aboutsaid shaft.

1. A device for use in a high-frequency heating apparatus having anenclosure made of conductive material into which highfrequency energy issupplied for heating material placed within the enclosure comprising: apair of blades of conductive material, means for mounting said bladeswithin said enclosure for rotation about a predetermined axis ofrotation, said blades being rotatable in succession into position tointercept a portion of the high-frequenCy energy supplied into theenclosure, one of said blades being positioned by said mounting means todirect high-frequency energy intercepted thereby in a centrifugaldirection with respect to said axis of rotation, the other of said pairof blades being positioned by said mounting means to directhigh-frequency energy intercepted thereby in the centripital directionwith respect to said axis of rotation, and said one of said bladesfurthermore is positioned for intercepting energy directed centripitallyfrom said other of said blades and directing a portion of saidcentripitally directed energy parallel to the axis of rotation.
 2. Adevice as recited in claim 1 wherein said blades of said pair thereofare mounted at diametrically opposite positions relative to the axis ofrotation and tangentially of the circumference of an imaginary circleconcentric with the axis of rotation and in a plane normal thereto, andsaid pair of blades are oppositely inclined with respect to the plane ofthe imaginary circle relative to the axis of rotation.
 3. The device asrecited in claim 2 wherein said blades lie in substantially parallelplanes inclined to the plane of the imaginary circle at an angle ofapproximately 45*.
 4. A device as recited in claim 2 wherein said bladesdefine planes intersecting the axis of rotation on opposite sides of theplane of the imaginary circle at angles of approximately 45*.
 5. Adevice as recited in claim 2 wherein said blades are each of elongatedconfiguration and are positioned along a given dimension thereoftangentially of the circumference of the imaginary circle.
 6. A deviceas recited in claim 1 wherein there is further provided at least oneadditional pair of said blades mounted on said rotary shaft with theblades of each pair diametrically disposed about said shaft and withsaid pairs of blades equiangularly disposed about said shaft.
 7. Ahigh-frequency heating apparatus comprising: an enclosure made of aconductive material, means for supplying high-frequency energy to saidenclosure, means for placing a heating load within said enclosure to beheated by the high-frequency energy, a movable device and meansincluding a rotary shaft to which said device is mounted for rotatingsaid device within said enclosure, said movable device includes a pairof conductive blades rotatable in succession into position to intercepta portion of high-frequency energy supplied to the enclosure, one ofsaid pair of blades directing high-frequency energy intercepted therebyin a centrifugal direction with respect to said rotary shaft and theother of said pair of blades directing high-frequency interceptedthereby in a centripital direction with respect to the rotary shaft, andsaid one of said blades furthermore is positioned for interceptingenergy directed centripitally from said other of said blades anddirecting a portion of said centripitally directed energy parallel tothe axis of rotation.
 8. Apparatus as recited in claim 7 wherein saidblades of said pair thereof are mounted at diametrically oppositepositions relative to said rotary shaft and tangentially of thecircumference of an imaginary circle concentric with the axis ofrotation of said shaft and in a plane normal thereto, and said pair ofblades are oppositely inclined with respect to the plane of theimaginary circle and axis of rotation.
 9. Apparatus as recited in claim8 wherein said blades are mounted by said mounting means to lie insubstantially parallel planes inclined to the plane of the imaginarycircle at an angle of approximately 45*.
 10. Apparatus as recited inclaim 8 wherein said blades define planes intersecting the axis ofrotation of said rotary shaft on opposite sides of the plane of theimaginary circle at angles of approximately 45*.
 11. Apparatus asrecited in claim 8 wherein said blades are positioned above a givendimension thereof tangentially of the cirCumference of the imaginarycircle.
 12. Apparatus as recited in claim 7 wherein said movable devicefurther includes at least one additional pair of said blades mounted onsaid rotary shaft with the blades of each pair diametrically disposedabout said shaft and with said pairs of blades equiangularly disposedabout said shaft.